The advent of arthroscopic surgery has revolutionized the field of joint surgery, most notably in the field of sports medicine with respect to surgery performed on the knee, perhaps the most vulnerable of human joints.
Generally, the word "arthroscope" refers to "viewing of the joint". Arthroscopic surgery involves the use of specialized tools which enable a surgeon to see the joint during surgery, without laying it open, as previously required. The ability to perform a surgical operation with very minimal intrusion into the joint reduces tissue trauma normally associated with surgical operations, thereby reducing previously required recovery and rehabilitation time.
Generally, to perform an arthroscopic surgery on a knee, for example, three surgical cuts are made. A tube is inserted into one of the cuts and saline solution is introduced into the joint through the tube. A tubular viewing scope is inserted into another one of these surgical cuts to allow a surgeon to actually view the joint. The viewing scope is often connected to a remote viewing screen to provide the surgeon with a better picture of the knee. Into the third of the surgical cuts is inserted a surgical cutting device to enable actual cutting of tissue that is to be removed from the joint. Initially, or for examination purposes, a surgical probe may be used, rather than a cutting device.
When arthroscopic cutting is required, it generally involves the removing of various types of tissue from the joint. This tissue can range from relatively soft synovial material which is attached to the walls of the joint to a relatively harder, gristle-like material, such as meniscal cartilage that may be found in the joint. An arthroscopic cutting device must be successful in shaving all of these types of tissue.
Because arthroscopic surgery entails only minimal intrusion into the joint through these three surgical cuts, the surgeon must perform within severely restricted space limitations. These space limitations often hinder access to the tissue to be cut and attempts to cut the tissue in an efficient manner.
Arthroscopic cutting devices have been designed with space limitations in mind. One typical arthroscopic cutting device has a housing designed to be hand held, an external tube projecting from the housing, a knife concentrically received within and rotatably mounted with respect to the external tube, a motor drivably connected to the knife and a motor controller. To provide cutting access for the rotatable knife, the external tube has a cutting port formed adjacent its free end. With respect to the external tube, the cutting port has circumferential and longitudinal dimensions so as to provide two opposing, oppositely directed, longitudinal edges. The longitudinal edges are adapted to cooperate with the rotating knife to shear tissue.
During arthroscopic cutting, the external tube is positioned within the surgical cut in order to project, in a relative manner, tissue through the cutting port. Rotation of the knife directs the tissue toward one of the longitudinal edges of the cutting port, where it is sheared between an edge and the rotating knife. Preferably, the rotatably mounted knife is tubular and in communication with a suction port formed in the housing. During cutting, suction is applied to the suction port to promote fluid flow of the saline. This draws tissue to be cut into the cutting port to facilitate shearing action and enable removal of discrete particles of tissue which have been cut.
One patent, U.S. Pat. No. 4,203,444, suggests that the knife provide two oppositely directed blades, each blade designed to cooperatively shear with one of the longitudinal edges of the cutting port during rotation in one direction. The motor is connected to the knife to provide bidirectional rotation of the knife. An initial direction of rotation may be selected, and subsequently reversed, to enable bidirectional cutting to take place. Bidirectional cutting enables the surgeon to remotely clean the instrument if it becomes jammed.
During bidirectional cutting, the location of shearing alternates between the two longitudinal edges, which results in faster cutting action. Otherwise, continuous rotation of the knife in the same direction eventually directs tissue beyond one longitudinal edge to a point where the blade no longer has cutting access. By reversing the direction of rotation of the knife, the tissue is directed back through the cutting port, toward the opposite longitudinal edge. While enroute to the opposite edge, the fluid flow pulls the tissue within the cutting port and the blade again has cutting access. A device which only rotates in one direction would have to be manipulated by the surgeon to produce the same effect. Such manipulation is undesirable from a practical standpoint.
The controller enables the surgeon to select a desired speed of rotation for the knife. U.S. Pat. No. 4,203,444, has cited advantageous cutting at speeds of rotation ranging from 100 rpm to 200 rpm.
Such bidirectional cutting requires a physical switching procedure to affect a reversal of the direction of rotation of the blade. Such a procedure, for example, might involve the simple flipping of a switch on the controller. Regardless, no matter how simple the procedure, the successive repetition of the same procedure is tedious and time consuming, and not desirable in an operating room environment.
Moreover, the reversal itself is also time consuming. The higher the speed of rotation of the motor, the greater the rotational inertia that must be overcome in order for rotation in one direction to stop, and rotation in the opposite direction to begin. Until this rotational inertia is overcome, the knife continues to rotate in the undesired direction. Meanwhile, the surgeon must wait for the reversal to occur before commencing arthroscopic cutting in the desired direction. In other words, if time is saved by cutting at higher speeds, that time is lost when the direction of rotation of the knife is reversed, and the surgeon must wait for reversal to take place.
Repetitive performance of the reversing procedure, coupled with the waiting period required for the motor to reverse itself, unnecessarily extend the duration of arthroscopic knee surgery. Additionally, the benefits of bidirectional cutting are limited by the tendency to cut at slower speeds, in order to reduce this waiting period.
It is therefore an objective of this invention to provide a bidirectional arthroscopic cutting device which does not require the performance of repetitive switching procedures in the operating room.
It is also an objective of this invention to provide a bidirectional arthroscopic cutting device having high speed cutting advantages without the disadvantages associated with waiting for reversal of rotation to occur.
It is a further objective of this invention to provide an arthroscopic cutting device which cuts with increased speed and efficiency.